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In industrial production processes, flow rate is a very important measurement parameter. There are many types of instruments available for measuring flow rate. Common ones include ultrasonic flow meters, electromagnetic flow meters, vortex flow meters, float-type flow meters, orifice plate flow meters, and so on. All of these flow meters share one common feature: they all measure volume, and their measurement accuracy is significantly affected by external factors such as temperature and pressure. In actual industrial production processes, people are more concerned about knowing the mass flow rate of the fluid flowing through pipes for various reasons such as energy savings, improved production efficiency, and better product quality; this is how the Coriolis mass flow meter came into being. It is based on the principle that when a fluid flows through a vibrating pipe, it exerts a force on the pipe walls that is proportional to the mass flow rate; this force is the Coriolis force. △t can be easily measured using phase detection technology; thereafter, the mass flow rate of the fluid flowing through the measurement pipeline can be calculated via signal processing circuits. Since the oscillation frequency of the measurement pipeline is inversely proportional to the fluid density, the fluid density flowing through the measurement pipeline can also be determined based on its oscillation frequency. In addition, a surface-mounted platinum resistor is usually installed on the wall at the inlet end of the measurement tube of the Coriolis mass flow meter. The temperature of the measurement tube is determined based on the resistance value of this platinum resistor, and using this temperature value, adjustments are made to parameters such as the elastic deformation coefficient K of the measurement tube system and the fluid density, thereby further improving the accuracy of mass flow measurement. Repair of common faults in Coriolis mass flowmeters: As Coriolis mass flowmeters are used more and more frequently, and a significant number of them operate in environments with high temperatures, high humidity, and corrosive conditions, coupled with the increased uncertainty in the power supply system due to the use of frequency converters, it is inevitable that these flowmeters will experience various types of faults. If it is possible to accurately determine the fault in the mass flow meter based on the observations at the site, and to provide prompt repair suggestions that allow the mass flow meter to be fixed quickly so that normal production can resume as soon as possible, this will save a great deal of time and improve productivity. It also avoids the need to purchase new equipment, thus saving a significant amount of working capital and greatly enhancing the efficiency of the factory. Below are several common faults and the corresponding repair solutions summarized by Henan Sanlin Mechanical and Electrical Equipment Co., Ltd. based on its over a decade of experience in maintaining Coriolis mass flow meters. Common faults: 1. Zero drift (common). 2. Inaccurate measurement data from the mass flow meter. 3. Unstable readings from the mass flow meter. 4. Blockage in the sensor’s measurement tube (this fault is rare). It should be noted that a distinct characteristic of this fault is an instantaneous display of the maximum flow rate; in such cases, it can be assumed that either the signal transmission cable is damaged or the sensor is faulty, and it is necessary to replace the cable or the sensor. If there is no AC or DC voltage at the drive terminal, it indicates that the fuse inside the transmitter has blown, and the circuit needs to be checked; after replacing the fuse, the device can be put back into operation ； If there is no alternating voltage but a direct current voltage, it indicates that the sensor is not oscillating. Possible causes and solutions: The sensor’s measurement tube is blocked; clear it first, then tap the sensor’s housing gently and measure the AC and DC voltages. If this still doesn’t work, the installation stress is too high – reinstall the sensor. When the flow rate increases, the flow meter indicates a negative increase. If everything checks out as normal, it indicates that the sensor’s flow direction is opposite to what the housing indicates, and the signal wires are connected reversely. At this point, simply change the installation direction and adjust the wiring of the signal lines. When the fluid is flowing, the flow rate shows positive and negative fluctuations; these fluctuations are significant, and at times it remains at a negative maximum value. Cause of the fault: ① The grounding resistance of the AC/DC shielding wires for power supply should be less than 4Ω; this helps to reduce fluctuations in line voltage due to changes in grid voltage and load voltage, thereby preventing impacts on the instrument circuits ； ②Pipeline vibration, on-site vibration sources, and the vibration of sensors can cause resonance, resulting in amplitudes that may be higher than normal ； ③The fluid has gas and liquid phase components ； ④There is a strong magnetic field or radio frequency interference around the transmitter. Solution: Re-grounding ； Replace the connection pipeline to the flow meter with a flexible metal hose ； Make an opening in the pipe above the flow meter and install a valve to discharge the gaseous components. (4) Stable at zero, but cannot return to zero. ①Installation issues ； ②The fluid temperature, density, and those of the calibration water differ significantly ； ③The sensor measurement tube is blocked. Solution: Increase or decrease the zeroing resistor. That is, when the zero point is always greater than 0, reduce the values of resistors R47 and R48 on the circuit board or increase the values of resistors R45 and R46; when the zero point is less than 0, do the opposite.